Phase Doppler method is a particle analyzer making use of the phase doppler principle of

 the laser doppler system to simultaneously measure the velocity and size of particles.

This measures average size, size distribution, average velocity and velocity distribution of particles as well.

Example

Average size, size distribution, average velocity and velocity distribution of particles of two 

fluid nozzles which spray by mixing air and water.

Figure out variability characteristics of average particle size in case of changing air-water volume ratio.